Method of preserving rubber



Patented Sept. 28, 1937 UNITED STATES PATENT OFFICE foot Corporation,Wilmington, De

tion of Delaware a corpora- No Drawing. Application July 25, 1934,Serial No. 736,968

11 Claims. (01. 18-50) This invention relates to the retarding of theageing of rubber; more particularly, to the use in rubber, balata, guttapercha, and other rubberlike materials of age retarders of the kindhereinafter set forth. The substances to which the invention relates arenew in themselves and have been found to protect against deteriorationfrom such influences as heat, light and oxygen. They have also beenfound to materially enhance the resistance of rubber to deterioration byflexing. In general, they accomplish various desirable ends, among them,that of imparting improved tensile strength to the treated rubberproduct.

It has heretofore been observed that certain aromatic hydroxy compoundssuch as phenol and beta naphthol when condensed with amines producecompounds which, upon their incorporation in unvulcanized rubber,improve the ageing properties of the resulting rubber product. Typicalof such materials are the compounds disclosed in United States PatentsNos. 1,781,306 and1,763,6 15.

Such materials before being used have always been purified to such anextent that generally only one cyclic compound remains in the productwhich is employed as the age retarder.

I This invention resides in the discovery that the compositeproductsobtained by condensing primary aromatic amines with alkyl substitutedmono hydroxy aromatic compounds in the manner hereinafter describedconstitute unusually satisfactory age retarders for rubber. While theconstitution of the'composite products of the invention' is not entirelyknown, the composite productsin question have been found to consist of amixture of materials in which a number can-be definitely identified-Where, for example, the

primary aromatic amine employed in the reaction may be'representedby'the formula R-NI-I and the alkyl substituted monohydroxy aromaticcompound by the formula R-OH wherein R comprises an alkyl substitutedaromatic radical, three of the principal materials embraced by thecomposite reaction product can be shown to have thestructural formulae(1) Rr-"NH-R, (2) 'R.-+NHR' and (3) R--,NH-R. Other products whichprobably form are tertiary amines of the formula V I Also, some of theammonia produced in the reactionis believed to react with the hydroxycom-- 55'; pound to give primary, secondary and possibly tertiaryamines. Further, in certain cases the hydroxy compound is converted toan ether.

In the case of commercially available alkylsubstituted hydroxy aromaticcompounds, such as commercial xylenols and commercial cresol or cresylicacid as it is often called, these products in themselves are complexmixtures. For example, there are available various grades of oresylicacid covering various distillation ranges, all of which are mixturescomprised of the isomeric cresols, and various xylenols. The commercialxylenols likewise are mixtures containing the isomeric cresols, a largerproportion of isomeric xylenols and still higher alkyl substitutedderiva tives. It is obvious, therefore, that for each individual hydroxycompound present in such mixtures, amine condensation products therewithwill contain each of the various types enumerated above.

It is believed that other high molecular. condensation products ofunknown constitution also form. In general, composite reaction productscontaining large proportions of the products represented by formulae(1), (2) and (3) are preferred. While the reaction splits out someammonia, the principal reaction is the removal of the hydroxy group fromthe. alkyl substituted hydroxy aromatic compound in' the form of water,a hydrogen atornfrom the amine supplying the necessary hydrogen to formthe water.

It is preferable to remove from the composite products any small amountsof inorganic impurities and the larger part of any ofthe more volatileprimary amines that may be present. The'removal of these primary aminesis especially desirable in case'the product is to be employed invulcanizable rubber compositions containing substituted or unsubstitutedmercaptan accelerators, as primary amines generally exert a pronouncedactivating effect on such accelerators. The precise manner of removal ofinorganic impurities and the more volatile primary amines may be anyknown to the art. In the case of the more volatile primary amines,either steam 'dis tillation of the composite product or extraction witha dilute acid such as dilute hydrochloric acid will in general be foundto be suitable.

. In preparing the composite products of the present invention, it isnecessary to effect a con-'- densation reaction with the attendantsplitting off of water. .For best results, it is desirable to employ asmall amount of a suitable condensation catalyst, generally in amountsfrom 0.1% to 1.0%, although larger quantities may be employed in certaincases. Itis not invariably necessary that a catalyst be employed,particularly if relatively high temperatures are used. The reaction ismost efiiciently carried out in a closed vessel and thus atsuperatmospheric pressures, although this feature likewise may beeliminated in certain instances. The temperatures required are upwardsof 200 C. and generally in the neighborhood of 300-350" C. The time ofreaction will vary some- What, but in nearly all cases a period of morethan five hours is necessary and sometimes as much as twenty-five hours.

The proportions of the reactants may be varied greatly although theproducts prepared from reactants in which the proportion of two mols ofthe primary aromatic amine to five mols. of the alkyl substitutedmonohydroxy aromatic compound have been found quite satisfactory.However, products in which the proportions are just reversed, namely,two mols. of alkyl substituted monohydroxy aromatic compound to fivemols. of primary aromatic amine have also been found quite satisfactory.Products prepared from various other proportions of the reactants havealso been found satisfactory. In fact, those prepared from as high asten mols of the primary aromatic amine for each mol. of the monohydroxyalkyl substituted aromatic compound have also been found to constitutevery satisfactory age retarders. Similarly products prepared from ashigh as ten mols. of the alkyl substituted monohydroxy aromatic compoundfor each mol. of the primary aromatic amine have also been quitesatisfactory.

The invention will be more fully described in and by the followingillustrative examples.

Example 1 To 540 parts by weight (5 mols.) of mixed cresols,commercially known as cresylic acid and comprising a mixture of mandp-cresols, boiling at 190215 C. at a pressure of 735 mm. are added 163parts by weight (1.5 mols.) of paraphenylene diamine and 50 parts byweight of zinc chloride. The mixture is heated in an autoclave for aperiod of approximately 12 hours and 40 minutes at a temperature of300-310 C. and at a pressure which rises to 650 pounds per square inchduring the reaction. The product is subjected to steam distillationwhereupon approximately 316 grams of material (principally unreactedcresols) are distilled off. The residue in the still is taken up inbenzene and poured into alcohol. 14.6 parts by Weight of crystals arefiltered off and discarded. The filtrate is then distilled to removesolvents and the residual product is distilled under reduced pressure.The portion boiling at 115-201 C. at 13 mm. pressure constitutes thecomposite product of the invention.

Example 2 To 216 parts by weight (2 mols.) of mixed cresols boiling at190-215 C. at a pressure of 735 mm. are added 465 parts mols.) ofaniline and 3.5 parts of zinc chloride. The mixture is heated in anautoclave for a period of 18 hours at a temperature of approximately 340C. The resulting mass is purified by stirring it thoroughly inapproximately 1000 parts of water, after which the oily residue isdistilled. The fraction collected between 135 C. .and 195 C. at apressure of 12 mm., in an amount of 121 parts and in the form of anamber colored oil constitutes the composite product of the invention.

Example 3 A composite mass of the products from six runs of thecresols-aniline reaction product similar to that prepared as describedin Example 2 was fractionally distilled, that portion boiling between185 and 255 C. at 55 mm. pressure being obtained in a 77.5% yield andconstituting the composite product of the invention.

Example 4 A mixture of 465 parts (5 mols.) of aniline, 7.9 parts of tintetrachloride and 328 parts (2 mols.) of paratertiary amyl phenol havinga boiling point of 159-160 C. at 50 mm. pressure and a freezing point of89 C. is heated for a period of 14 hours at a temperature ofapproximately 340 C. The crude product is distilled, the fractioncollected between 185-255 C. at 50 mm. pressure being obtained in theform of a dark green fluorescent liquid. This fraction, the compositeproduct of the invention, is obtained in a yield of 225 parts.

Example 5 A mixture of 198 parts (1 mol.) of crude p-p diamino diphenylmethane, 6.3 parts of tin tetra chloride and 432 parts (4 mols.) ofmixed cresols is heated in an autoclave for a period of 14 hours at atemperature of 340 C. The product is then distilled, that portionboiling below 225 C. at 737 mm. pressure being discarded. The residue ofapproximately 240 parts is washed by treating it with 1000 cc. of Waterand 100 cc. of concentrated hydrochloric acid. Upon being filtered andthoroughly rewashed with waterfthe composite product of the invention isobtained in a yield of approximately 231 parts in the form of a darkbrown, very viscous oil.

Example 6 To 244 parts (2 mols.) of mixed xylenols are added 535 parts(5 mols.) of orthotoluidine and 3.5 parts of tin tetrachloride,SnCl4.5H2O. The mixture is heated in an autoclave for a period of 12hours at a temperature of 340 C. The product is then distilled, thatportion boiling below 250 C. at atmospheric pressure being discarded.The total residue, which is the composite product of the invention, isobtained in the form of a black liquid. It is insoluble in water andsoluble in benzol.

Example 7 To 375 parts (3.5 mols.) of paratoluidine are added 5.2 partsof tin tetrachloride and 151 parts (1.4 mols.) of mixed cresols, 50% of.whichboil at 212 C. The mixture is heated in an autoclave for a periodof ten hours at a temperature of 340 C. The product is then distilled,the portion boiling between 180-250 C. at 12 mm. pressure being retainedas the composite product of the invention. A yield of approximately 214parts of a semicrystalline, soft mass is obtained. 4

Example 8 A mixture of 500 parts (3.5 mols.) of alpha naphthylamine, 151parts (1.4 mols.) of mixed cresols and 6.5 parts of tin tetrachloride isheated in an autoclave for a period of approximately 12 hours at 340 C.The product is washed thoroughly with water and hydrochloric acid inorder to make it faintly acid to remove the tin. It is then filtered anddistilled. The product boiling above 215 C. at 12 mm. pressure is in anamount of 319 parts, is in the form of a dark brown tarry mass andconstitutes the composite product of the invention.

Example. 10

To, 200 parts (1.4 mols.) of alpha naphthylamine are added 427 parts(3.5 mols.) of mixed xylenols and 6.3 parts of tin tetrachloride. Themixture is heated for a period of 12 hours at 340 C. The product iswashed thoroughly with water and sufficient hydrochloric acid to makefaintly acid, filtered and distilled. The residue boiling above 215 C.at 10 mm. pressure is in the form of a black-brown tar and constitutesthe com- .posite product of the invention.

Example 11 a dilutesodium hydroxide solution, whereuponthe amines intarry form are obtained. Upon being washed and dried, partsby'weight ofthese mixed amines are mixed with 432 parts (4 mols) of mixed cresolsand 5 parts of tin tetrachloride. The mixture is heated in an autoclavefor a period of 12 hours at 340 C., whereupon the product is filteredand distilled, the residue boiling above 250 C. at 734 mm. pressurebeing obtained in the form of a black hard tar and constituting thecomposite product of the invention.

. It will be understood that these examples are but illustrative of theinvention and that numerousother composite products of primary are maticamines and alkyl substituted monohydroxy aromatic compounds may besimilarly prepared. Another example which has been found to be a verysatisfactory age retarder for rubber is that obtained by condensingfive'mols. of orthotoluidine with two mols. of mixed cresols in themanner previously described, the composite product of the inventionbeing that product boiling between and 225 C. at 12 mm. pressure.

Examples of hydroxy compounds which may be employed in the practice ofthe invention in lieu of those mentioned aboveare the various isomers ofisopropyl phenol, ethyl phenol, n-butyl phenol, n-propyl phenol,isobutyl phenol, n-amyl phenol, isoamyl phenol, cyclohexyl phenol,cyclo-- pentamethylene phenol, diethyl phenol, 'di-n-- propyl phenol,di-n-butyl phenol, di-isoamyl phe nol, etc. 7

Similarly, numerous other primary aromatic amines maybe substituted forthe primary amines given in the above examples. Illustrative are thexylidines, the amino phenols, the amino cresols such as o-amino mcresol, the amino naphthols, diamino phenyl naphthyl ether, alphafurfuryl amine; wtetrahydr'oalpha furfuryl: amine, beta naphthylamine',alpha aryl tetrahydronaphthylamine, beta aryl tetrahydronaphthylamine,cy-., clohexyl amine, alpha Still others are para amino biphenyLp-p'diamino diphenyl methane, p-p diamino ditolyl methane,2-4-diaminodiphenyl amine, p-amino diphenyl amine, Z-amino fiuorene,2-l-diamino fluorene,. cumidinie; 'benzidine, tolidine; thephenetidines, the anisidines, 3-amino acenaph thene, 1'-amino amine,meta toluidine, meta tolylene diamine; and the several naphthalenediamineso Likewise instead of the condensation catalysts previouslydisclosed, any other such catalyst may be employed, examples beingiodine, sodium bisulphate, potassium bisulphate, titanium chloride,ferricchloride, aluminum fluoride and aluminum bromide.

While the composite products of this invention are in and of themselvesexcellent age retarders, they may be employed, if desired, inconjunction with other materials. Also, various derivatives of thesecomposite products have been found to be suitable age retarders.Exemplary are the nitrosamine, ketone, aldehyde, and sulphurderivatives. Illustrative of such are the following examples:

Example 12 36.5 parts of the composite product of aniline and mixedcresols boiling between 155 and 255 C. at 18 mm. pressure preparedsimilarly to the manner described in Example 2 are dissolved in 125parts of ethyl alcohol. added 20 parts of concentrated hydrochloric acidand 8.3 parts :of an aqueous 36% formaldehyde solution. The mixture isallowed to stand for av short period and is then diluted with water.

alicyclic tetrahydronaph thylamineand beta methyl alpha naphthylamlne;

Z-methyl naphthalene, di(pamino phenyl) 2-2-propane, meta phenylene, di-

To this solution are.

An oily product comprising 38 parts separates out and is washed anddried. It is in the form of a brown plastic mass.

Example 13 92 parts of the composite product ofaniline and mixed cresolsprepared as described in Ex-;

ample 3 are mixed with 32 parts of sulphur, heated to 180-185" C. andtreated with .5 part of iodine. The heating is continued for a period of12 minutes at atemperature of -215 C. a The mixture is allowedto cool,whereupon the un-- reacted sulphur crystallizes out. After filtering,

the composite product derivative is obtained in the form of a brown oilwhich is soluble in organic solvents and insoluble in water.

Y "Example-1 4 I 'Ihcp'artially sulphuriaed derivatives of the compositeproducts may also be employed as age retarders. In one example 92 partsof a composite product of aniline and mixed cresols. are fixed with 4.8parts of sulphur, heated to 180 C. and treated with .5 part of iodine.The. heating perature ranging from 180 C. to 215C. On cooling, the,composite product derivative isa brown oil which may as an age retarder.

is continued for a period of 12 minutes at. a tem be employed in suchform a period of 20.5 hours at a temperature of 220 225 C. The crudeproduct is subjected to distillation and that portion boiling at 200 C.at 736 mm. pressure, which comprises the composite product derivative ofthe invention, is obtained in approximately 384 parts.

Example 16 pressure had risen to 900 pounds per square inch.

and the temperature to 347 C. The product, after cooling, was washedwith water, decanted and distilled. The residue boiling above 250 C. at740 mm. pressure is in the form of a dark brown oil and constitutes thecomposite product derivative of the invention.

Example 17 It is also possible to first react the acetone with the mixedcresols and afterwards react the resulting product with the primaryamine. Thus 432 parts (4 mols.) of mixed cresols, 116 parts (2 mols.) ofacetone and 5.5 parts of tin tetrachloride are heated in an autoclavefor a period of 6.75 hours at a temperature of 340 C. The resultingproduct is cooled, whereupon 265 parts thereof are removed from theautoclave. To the mass remaining in the autoclave are added 372 parts (4mols.) of aniline and 3.7 grams of tin tetrachloride. This mixture isheated for a period of 12 hours at 340 C. The product is then dilutedwith ether, filtered and fractionally distilled. That portion boilingabove 250 C. at 740 mm. pressure constitutes the composite productderivative of the invention, is in the form of a dark brown oil and in ayield of 214 parts.

Example 18 In preparing the aldehyde derivatives of the compositeproducts of the invention, it is also possible to first react the alkylsubstituted monohydroxy aromatic compound with the aldehyde and thenreact the resulting product with the amine. Illustrative of thisprocedure is the example in which 216 parts (2 mols.) of mixed cresolsare reacted at a temperature below 70 C. with 32 parts (1 mol.) offormaldehyde and a trace of hydrochloric acid. The product is a viscousamber oil. The product is believed to be mixed methylene dicresols. 115parts (0.5 mol.) of these mixed methylene di-cresols, 465 parts (5mols.) of aniline, and 2.9 parts of tin tetrachloride are heated in anautoclave for a period of 8 hours at 340 C. The product is filtered toremove inorganic impurities and distilled to eliminate low boilingconstituents. The portion boiling above 250 C. at atmospheric pressures,constituting the composite product derivative of the invention, may beemployed to good advantage for the retarding of the ageing ofdeteriorable hydrocarbon compositions.

Example 19 Another derivative of the composite products of the inventionis that in which toluhydroquinone is employed. A mixture of 465 parts (5mols.) of aniline, 216 parts (2 mols.) of mixed cresols, 6 parts oftoluhydroquinone and 6.9 parts of tin tetrachloride is heated in anautoclave for a period of 12 hours at 340 C. The product is di lutedwith ether, filtered and distilled to eliminate low boilingconstituents. The portion boiling above 250 C. at 740 mm. pressureconstitutes the composite product derivative of the invention and may beemployed as an age retarder as herein described.

Erample 20 Another composite product derivative of the invention is thatin which 8 parts of thiophenyl beta naphthylamine are dissolved in 92parts of the product of Example 3 by warming the mass. The cooledproduct is a greenish brown oil and constitutes the composite productderivative of the invention.

Example 22 The nitroso derivatives of ucts of the invention are alsoexcellent age retarders. One such derivative which has been found quitesatisfactory is that obtained by nitrosating a composite productprepared by heating in an autoclave for a period of 18 hours at atemperature of 340 C. 465 parts of aniline, 216 parts of mixed cresolsand 3.5 parts of AlCl3 and eliminating by distillation the portion ofthe the composite prodproductboiling below 155 C. at 18 mm. pressure andabove 205 at 18 mm. 300 parts of this composite product are dissolved in700 parts of alcohol and treated with 205 parts of hydrochloric acid(specific gravity 1.18). The resulting solution is cooled to -5 C. andmaintained at this temperature while 131.5 parts of sodium nitritedissolved in 260 parts of water are added slowly thereto, meanwhileagitating the mass. The mixture after standing one half hour is dilutedwith one and one half times its volume of water whereupon a dark brownoily layer forms. This oily layer, which is the nitroso derivative ofthe composite product of aniline and mixed cresols and constitutes thecomposite product derivative of the invention, is separated, washed withwater and dried. It then may be employed as an age retarder ashereinafter described.

The composite products of this invention and their various derivativesmay be employed to advantage as age retarders for rubber. They may beemployed advantageously in substantially any of the standard rubberformulae, the following being one in which they have been found to givegood results.

Parts by weight Extracted pale crepe rubber 100 Zinc oxide Sulphur 3Stearic acid 1.5 Hexamethylene tetramine 1 Age retarder 1 Rubber samplesprepared in accordance with the foregoing formula were subjected tovulcanization for varying periods of time and then tested to ascertaintheir physical characteristics.

2",o94;2ee

Itis evident from the following table that rub-- One set from each typeof stock was tested'immediately for tensile strength and elasticitywhile a second set was subjected to aging ina- Bierer-Davis bomb for 6days in oxygen at 50 C.,

her compositions containing even small proportions of the age retardersof this invention resist deterioration remarkably well. Similar comand150 pounds per square inch. At the com positions not containing the ageretarders, upon 5 clusion of the 6 day period, the samples were rebeingsubjected to corresponding tests, increase moved from the bomb andsubjected to physical in weight in the neighborhood of 10% and lose.tests corresponding to those conducted upon the almost all their tensileand elongation properties. unaged samples. The following data wereobtained: I

Original Aged ,7 V f, Pct.

'mt' M Load lIgs/em mt M Load kgs/cm yvt. ax; ax; Y inc; tens. elg. tenselg. 15 500% 700% 500% 700% Reaction product of mixed cresols andp-phenylene diamine (Example 1) Reaction product of mixed cresols andaniline (Example 2) Reaction product of mixed cresols and aniline(Example 3) s5 2s5 76 880' r 11 2s 84 850 13 as .22 30 Reaction productof p-tertiary'amyl phenol and aniline (Example 4) Reaction product ofmixed cresols and p-p-diamino diphenyl methane (Example 5) i e 40 35I285104 910 12 32 111 850 14 45 .10 50 120 845 16 51 128 805 19 69 11. 70-;139 790 21 78 132 750 ,25 100 .17

Reaction product of mixed xylenols and o-toluidine (Example 6) Reactionproduct of mixed cresols and p-toluidine (Example 7) 50 of mixedrcresols and alphanaphthylamine (Example 8) 55 905 11 30 104 865 12 40.06 t 745 20 88 n .126 800 18 66 .12. .795 22 l 76 141 7 50 24 100 .14

-Reaction product of mixed cresols and alpha naphthylamine (Example 9} 035/285.. 91 890 11 V 30 106 Y 855 14 41 .13 109 770 19 71 115 740 24 .16129 785 21 V 77 .138 7.60 25 ;18

W Reaction product of mixed xylenols and alpha naphthylamine. (Example10) 65 Reaction product of mixed cresols and mixed amines (Example 1 1)'v 70 Y 35/2s5. 62 785 13 r 40 825 16 52 .07 50 102 780 19 64 124 785 2278 .08 131 760 24 90 133 735 29 i .16

Original Aged Pct. Ult M Load kgs/cm Load kgs/cm wt. ax. me. 5 Cure inmine. tens. Ult. Max. .5v

Formaldehyde derivative of mixed cresols-aniline (Example 12) 1O 35/2s595 900 12 30 76 850 12 V 31 .14

Sulphur derivative of mixed cresols-aniline (Example 13) Sulphurderivative of mixed cresols-aniline (Example 14) Acetone derivative ofmixed ctesols-aniline (Example 15) 25 25 30 Reaction product of mixedcresols, aniline and acetone (Example 16) 30 35 Reaction product ofmixed cresols and aniline acetone (Example 17) 35 40 Reaction product ofmixed methylene dicresols and aniline (Example 18) 40 45 Reactionproduct of mixed cresols, toluhydroquinone and aniline (Example 19) 45 Q94 840 14 43 105 800 18 60 07 115 820 17 58 111 765 21 76 15' 130 750 25Y 94 137 740 30 110 I 20 Mixture of tolu hydroquinone and mixedcresols-aniline (Example 20) 50 Mixture of thiophenyl beta naphthylanuneand mixed cresols-anilme (Example2l) Nitroso derivative of mixedcresols-aniline (Example 22) From the foregoing it is evident that thecom- Other advantages are that by carrying out the posite productsherein disclosed are highly suitprocedure herein disclosed age retardersare obable as age resisters of rubber. Not only do the tained in anincreased yield since the total usable 70 products of the presentinvention counteract the product is two or three times the quantity of aeiTects of the influences of heat, light and oxygen, single component.Furthermore, the composite but they tend to impart other highlydesirable "products generally possess a lower melting point qualities.such, for example, as increased resistthan. the separate componentsthereof which ance to deterioration by flexing. i could be obtained andtherefore disperse more 75 readily in rubber during the processingoperations. Still another distinct advantage is that while a number ofthe individual compounds which are known to be present in the compositeproducts possess a pronounced tendency to bloom in rubber stocks, thecomposite products hardly exhibit this tendency at all.

It is to be understood that as hereinafter used the term benzenoidembraces phenyl and naphthyl groups, which, as preferred, do or do notcontain substituents, such substituents being, for example, alkyl,alkoxy and like groups. Also, by the term rubber it is meant to includerubber, synthetic rubber, latex, balata, gutta percha, guayule, rubberisomers, rubber conversion products and similar materials. It will beapparent that numerous changes may be made in the procedure to befollowed and the chemicals employed without departing from theinventiveconcept.

It is intended that the patent shall cover, by suitable expression inthe appended claims, whatever features of patentable novelty reside inthe invention.

What I claim is:

l. The processof preserving rubber which comprises incorporating thereina composite product obtained by condensing a primary aromatic amine withmixed cresols while splitting off water.

2. The process of preserving rubber which comprises incorporatingtherein a composite product obtained by condensing aniline with mixedcresols while splitting off water.

3. An age-resisting rubber composition comprising rubber and a compositeproduct obtained by reacting in a closed vessel at a temperature of atleast 200 C. for a period of at least five hours aniline with mixedcresols in the presence of a condensation catalyst and removing the morevolatile primary amines.

4. An age-resisting rubber composition having incorporated therein acomposite product resulting from the condensation of mixed cresols withaniline while splitting off water.

5. A rubber product that has been vulcanized in the presence of acomposite product resulting from the condensation of aniline with mixedcresols at a temperature of at least 200 C. for a period of at leastfive hours in the presence of a small amount of a condensation catalyst.

6. The process of preserving rubber which comprises incorporatingtherein a composite product obtained by condensing a primary aromaticamine with a material selected from the group consisting of mixedcresols and mixed xylenols while splitting off water.

'I. The process of preserving rubber which comprises incorporatingtherein a composite product obtained by condensing a primary aromaticamine with mixed xylenols while splitting off water.

8. An age-resisting rubber composition comprising rubber and a compositeobtained by condensing a primary aromatic amine with mixed cresols whilesplitting off water.

9. The process of preserving rubber which comprises incorporatingtherein a composite product obtained by reacting in a closed vessel at atemperature of at least 200 C. for a period of at least five hoursaniline with mixed cresols in the presence of a condensation catalystand removing the more volatile amines.

10. An age-resisting rubber composition comprising rubber and acomposite product obtained by condensing a primary aromatic amine with amaterial selected from the group consisting of mixed cresols and mixedxylenols while splitting off water.

11. An age-resisting rubber composition comprising rubber and acomposite product obtained by condensing a primary aromatic amine withmixed xylenols while splitting ofi water.

ALBERT M. CLIFFORD.

